The deterioration in regimen adherence and metabolic control associated with the adolescent developmental period is well known. However, a subset of high-risk adolescents with diabetes demonstrate much more serious adherence problems, as evidenced by chronically poor metabolic control (CPMC). Adolescents with CPMC represent a group at high risk for short and long-term diabetes complications and are therefore heavy users of both medical resources and health care dollars. Minorities are also over-represented among adolescents with CPMC. However, such adolescents are infrequent users of outpatient health services and traditional office-based approaches have been largely unsuccessful in improving adherence and metabolic control in this group. In addition, there are few clinical trials targeting high-risk adolescents. This competing renewal application represents the next step in our programmatic research to improve health outcomes for such at-risk, urban youth. Multisystemic Therapy (MST) is an intensive, home-based family therapy originally used with youths presenting with serious mental health problems and their families. Our group has now demonstrated the efficacy of MST for the improvement of regimen adherence and metabolic control and reduction of DKA admissions among adolescents with CPMC. However, our initial investigation identified two variables, number of parents in the home and adolescent overweight,that significantly affected study outcomes. The proposed investigation is a randomized controlled trial enrolling 170 participants that compares the effectiveness of an enhanced version of MST as compared to a telephone support (TS) intervention to treat CPMC in adolescents with insulin-managed diabetes. The MST- Enhanced (MST- ENHC) intervention includes two new modules: one for adherence to a weight loss program and one for building social support for single parents. Therefore, this new trial will allow us to test whether targeting adherence to weight loss recommendations in addition to adherence to more traditional aspects of the diabetes regimen will improve our ability to normalize HbA1c and whether targeting social support will improve the stability of improvements in adherence for single-parent families. If successful, MST will provide immediate assistance to a vulnerable population at high risk for diabetes complications and reduced quality of life.